creating commit or tag objects, or
	when writing reflogs. See linkgit:git-commit[1] for valid formats.

`EMAIL`::
	The email address used in the author and committer identities if no other
	relevant environment variable or configuration setting has been set.

Git Diffs
~~~~~~~~~
`GIT_DIFF_OPTS`::
	Only valid setting is "--unified=??" or "-u??" to set the
	number of context lines shown when a unified diff is created.
	This takes precedence over any "-U" or "--unified" option
	value passed on the Git diff command line.

`GIT_EXTERNAL_DIFF`::
	When the environment variable `GIT_EXTERNAL_DIFF` is set, the
	program named by it is called to generate diffs, and Git
	does not use its builtin diff machinery.
	For a path that is added, removed, or modified,
	`GIT_EXTERNAL_DIFF` is called with 7 parameters:

	path old-file old-hex old-mode new-file new-hex new-mode
+
where:

	<old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the
                         contents of <old|new>,
	<old|new>-hex:: are the 40-hexdigit SHA-1 hashes,
	<old|new>-mode:: are the octal representation of the file modes.
+
The file parameters can point at the user's working file
(e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file`
when a new file is added), or a temporary file (e.g. `old-file` in the
index).  `GIT_EXTERNAL_DIFF` should not worry about unlinking the
temporary file -- it is removed when `GIT_EXTERNAL_DIFF` exits.
+
For a path that is unmerged, `GIT_EXTERNAL_DIFF` is called with 1
parameter, <path>.
+
For each path `GIT_EXTERNAL_DIFF` is called, two environment variables,
`GIT_DIFF_PATH_COUNTER` and `GIT_DIFF_PATH_TOTAL` are set.

`GIT_EXTERNAL_DIFF_TRUST_EXIT_CODE`::
	If this Boolean environment variable is set to true then the
	`GIT_EXTERNAL_DIFF` command is expected to return exit code
	0 if it considers the input files to be equal or 1 if it
	considers them to be different, like `diff(1)`.
	If it is set to false, which is the default, then the command
	is expected to return exit code 0 regardless of equality.
	Any other exit code causes Git to report a fatal error.


`GIT_DIFF_PATH_COUNTER`::
	A 1-based counter incremented by one for every path.

`GIT_DIFF_PATH_TOTAL`::
	The total number of paths.

other
~~~~~
`GIT_MERGE_VERBOSITY`::
	A number controlling the amount of output shown by
	the recursive merge strategy.  Overrides merge.verbosity.
	See linkgit:git-merge[1]

`GIT_PAGER`::
	This environment variable overrides `$PAGER`. If it is set
	to an empty string or to the value "cat", Git will not launch
	a pager.  See also the `core.pager` option in
	linkgit:git-config[1].

`GIT_PROGRESS_DELAY`::
	A number controlling how many seconds to delay before showing
	optional progress indicators. Defaults to 2.

`GIT_EDITOR`::
	This environment variable overrides `$EDITOR` and `$VISUAL`.
	It is used by several Git commands when, on interactive mode,
	an editor is to be launched. See also linkgit:git-var[1]
	and the `core.editor` option in linkgit:git-config[1].

`GIT_SEQUENCE_EDITOR`::
	This environment variable overrides the configured Git editor
	when editing the todo list of an interactive rebase. See also
	linkgit:git-rebase[1] and the `sequence.editor` option in
	linkgit:git-config[1].

`GIT_SSH`::
`GIT_SSH_COMMAND`::
	If either of these environment variables is set then 'git fetch'
	and 'git push' will use the specified command instead of 'ssh'
	when they need to connect to a remote system.
	The command-line parameters passed to the configured command are
	determined by the ssh variant.  See `ssh.variant` option in
	linkgit:git-config[1] for details.
+
`$GIT_SSH_COMMAND` takes precedence over `$GIT_SSH`, and is interpreted
by the shell, which allows additional arguments to be included.
`$GIT_SSH` on the other hand must be just the path to a program
(which can be a wrapper shell script, if additional arguments are
needed).
+
Usually it is easier to configure any desired options through your
personal `.ssh/config` file.  Please